This paper presents an experimental study to characterize fluid leakage through a rough metal contact The focus is on an original experimental setup and procedure designed to measure the fluid micro (or nano) leak rate with great precision over several orders of magnitude Liquid leak-rate measurements were carried out under two distinct operating conditions, ie, in the case of a pressure gradient applied between contact edges and in the case of a pure diffusive effect resulting from a species concentration gradient Experimental leak-rate results are discussed in terms of effective contact permeability—or transmissivity—and in terms of effective contact diffusivity versus contact tightening

Experimental Leak-Rate Measurement Through a Static Metal Seal

SUMMARY This paper presents a unified optimization approach for the selection of the machining parameters that provide the maximum metal removal rate for any specified surface quality and tool life. The approach is based on models presented by Jang and Seireg (1989, 1990) for predicting surface roughness, maximum cutting temperature and residual stress distribution on the machined surface and utilizing machine tool parameters and cutting conditions. Numerical results show that the procedure can be used to considerable advantage in specifying the machining variables for developing the decision-making database of the machining process. The present unified model is proposed to represent a strategy for a robust adaptive control system in a machining process.

A unified optimization model of a machining process for specified conditions of machined surface and process performance

The surface characteristics of machined Inconel-718 nickel-base superalloy were investigated using natural and controlled contact length tools, at various cutting speeds, and under both dry and lubricated conditions. Surface damage in the form of cavities and holes, fractured areas, and long and short straight grooves parallel to the direction of cutting was produced when machining was carried out at low cutting speeds and with tools having natural or controlled contact length, and at high cutting speeds with tools having natural contact lengths. The intensity of surface damage and total area affected decreased as the cutting speed was increased. The quality of the machined surface was drastically improved at high cutting speeds, when tools having controlled contact lengths were used. The application of lubricants was less effective for improving the surface quality. The results were interpreted in terms of the mechanics of chip formation, the interaction between the tool-nose region and freshly machined surface, and the tool forces resulting from the machining process.

Surface characteristics of machined Inconel-718 nickel-base superalloy using natural and controlled contact length tools

This paper presents a comparison of the performance characteristics of TiN (Titanium nitride) and ZrN (Zirconium nitride) coatings on split point drills. The objective of this work was to choose the better coating for machining tough materials like INCONEL. This leads to an increased productivity of drilling holes in certain components of environmental control systems and fuel control systems (in aerospace industry) made of tough materials like INCONEL. The comparison of the performance characteristics was based on the measurement of the mean values and dynamic fluctuations of the cutting force and the number of holes drilled under the same optimum machining conditions. The measurements were carried out using two specially designed piezoelectric dynamometers. The dynamometer was calibrated from static and dynamic outputs and techniques were employed for increasing the measuring accuracy and reducing the cross interference by obtaining the elements of the tranfer function. Power spectrum plots of the drift force, axial force and torque were obtained so that these plots may be used as a signature. Results show that the ZrN coating is better than the TiN coating because (a) the mean values of the axialforce, drift force and torque are smaller, thus improving the roundness, (b) the dynamic flutuations of the forces and torque about the mean are smaller thus improving the surface quality of the holes produced, (c) the number of holes before the failure of the drill is about three times more for a ZrN coated split point drill as compared to a TiN coated drill.

An experimental investigation into the comparison of the performance characteristics of TiN and ZrN coatings on split point drills using the static and stochastic models of the force system as a signature

One of the serious problems in automated chip-removal processes is the prediction of tool changing time. Tool change before the end of its useful time causes an increase in tool cost. Late changes, on the other hand, cause dimensional inaccuracies and surface finish deterioration on the workpieces and an increase in the energy consumption. Therefore, it is aimed in this work to present an in-depth study of the effects of cutting parameters on various force ratios and to determine their applicability for tool condition monitoring in turning processes.

A.K. Rakhit

Papers

The influence of metal cutting forces on the formation of surface texture in turning